A spread spectrum detector employs a Doppler phase correction system that improves
correlation of pseudo-noise (PN) codes to a received spread spectrum signal by
combining phase shifts, in the time domain, to correlation values that compensate
for the Doppler shift error that is inherent in the signal and that is imposed
upon the signal by movement between the signal source and receiver. In architecture,
the Doppler phase correction system includes a receiver to receive a spread spectrum
modulated signal having the Doppler shift error, a multiplier to produce a plurality
of complex first correlation values based upon the signal and a code. A phase shifter
generates a plurality of complex second correlation values respectively from the
first correlation values. The second correlation values being phase shifted by
respective different amounts from corresponding first correlation values, so that
the second correlation values exhibit less of the Doppler shift error than the
first correlation values. The phase shifter can be implemented with a look-up table
that stores a plurality of phase shift values, a counter that produces indices
for the look-up table, and a multiplier that multiplies the phase shift values
that are output from the look-up table with the first correlation values to produce
the second correlation values. Finally, a combiner, such as an integrator, combines,
or integrates, the second correlation values to derive a third correlation that
indicates a degree of correspondence of the code with the signal.